1. Field of the Invention
The present invention relates to a polychromator type spectroscope and, more particularly, to the improvement in its spatial resolving power.
2. Description of the Related Art
A spectroscope is intended to widely disperse the light ranging from the ultraviolet region to the visible light region. To this end, a mirror is used as the condenser optical system. However, a conventional type mirror spectroscope had the drawbacks such as (1) that in which the imageability differs between the center and peripheral part of the light-receiving surface and the performance at the peripheral zone is poor, (2) that in which the aperture ratio is inferior, etc. Also, regarding the use of a lens, in many cases, it is not used for the reason that the ultraviolet region becomes unable to be measured. Generally, therefore, an endeavor to obtain a high level of spatial resolving power by improving the mirror has hitherto been made and, in this view, a spectroscope using toroidal mirrors or the like have hitherto been developed. (For example, see the Japanese Patent Application Laid-Open No. 2003-42846)
Also, by arraying the optical fibers in a row in the incident slit of the polychromator, the light rays from a number of points are spectrally simultaneously measured. The light rays from the respective optical fibers are dispersed through the action of the diffraction grating and thereby these light rays are imaged on the light-receiving surface of the two-dimensional detector. However, as described above, in the conventional spectroscope, since the spatial resolving power is low and the images in the slit direction are widely spread, there was a problem in that the images of the light rays from the respective optical fibers overlap one another. Also, even in the spectroscope in which to correct the above-described astigmatism with use of a toroidal mirror or the like, the manufacturing cost is incurred and, in terms of the performance as well, it was not satisfactory.